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My First PSII - Estes Ventris Build

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lcorinth

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I started this rocket a few days before beginning the Nike Smoke build, and a couple weeks before starting the Leviathan build. While the Nike Smoke is built and just needs paint, and the Leviathan is ready to fly (for an L1 cert), the Ventris has taken me a little longer. Heck, they all took a long time, as I chipped away at them bits at a time.

I opened the package a year ago today, and laid out the parts. Nice looking kit!

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The payload section is a little small.

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I took a while to consider what I'd fly in this thing - a camera? Some kind of hot wire cutter for deployment? If need be, I could enlarge the payload by cutting open the base of the nose cone (in the end, I decided I'd just use a Jolly Logic altimeter, so there's plenty of room. I have three of these, so I can consider different options on different builds).

I really like the fins on the Ventris...

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But I had to think about what to do with these. I tend to shape the fins on my smaller rockets. Rounding or beveling the leading edges of these would be simple, but with the curved trailing edge, I wasn't so sure. Maybe I'd try it, maybe not. I have streamlined balsa fins with curved trailing edges before, on a couple of Cosmic Explorers, and they look pretty nice.

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And I did manage to do the same with plywood fins, on the Leviathan build:

[video=youtube;AI2jtedVBwI]https://www.youtube.com/watch?v=AI2jtedVBwI[/video]

But since I have three of these, I decided to keep it simple, and leave the fins square.

The launch lugs on the Ventris come with balsa standoffs, about 1/4 inch high, made from two pieces of balsa you glue together.

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For this rocket, I wanted to use some of the mini-buttons from rail-buttons.com, which fit a metric rail. I have one, and one of our club members also has one, which can clamp right onto our 1010 rails. So, I'd need to figure out how to make a standoff. If I tried to use the balsa here, I would probably just split it in two.

I sanded the motor tube, and as per instructions, stretched out the green paper "spacer ring" by pressing it down over the nose cone. Finally, as I always do, I marked the forward and aft ends of the motor tube.

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lcorinth

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OK, motor mount!

Using the green paper spacer ring, I started by placing the middle centering ring, which I then tacked into place with thick CA.

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I followed this with the forward and aft centering rings.

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Now that I look back at these pictures, I'm not sure why I bothered tacking on the aft CR, because I then removed it before installing the MMT into the rocket.

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Anyway, I filleted the middle and forward centering rings on both sides with wood glue (forgot to photograph). Next, I installed the motor mount using Bob Smith 30 minute epoxy. I used two fins to get a tight fit - with the aft end of the fin tab all the way back in the slot, the fin trailing edge root would be precisely flush with the aft of the airframe. The middle centering ring would be tight against the forward end of the fin tab, making a nice tight fit. You can see that the fin slot is slightly longer than the fin tab, because the middle CR can be seen just peeking through the slot on the forward end.

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I taped the body tube in an upright position to a leg of my metro shelving unit, so the epoxy could cure without running.

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Next up, the coupler...
 

lcorinth

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Around when I was starting the Ventris I saw this thread. You can see from the post that this guy made a "laundry shelf" in the coupler to keep the chute from sliding too far back into the tube.

I thought that was neat, but I thought I'll probably not cut that right. Still, I kept thinking about it.

For some reason, I thought it might be easier to make a baffle. I'm not great at cutting circular shapes freehand, but I gave it a shot.

All I had on hand at the time was 1/16 inch basswood - easy to cut, but pretty thin. Still, I traced the coupler onto the basswood. I made four circles - because the wood was so thin, I decided to double it up. If I could get a good fit, I'd go for it. If not, I'd abandon the idea and skip the baffle.

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I cut out the circles with a hobby knife, and then cut them in two, leaving a little more than half of each circle, to make a "half-moon" baffle. I have only used one baffle before, in my 3D Rocketry Nautilus II. I like it, because with the half moons, it's easy to shake out any debris from the ejection after flight.

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They're not perfect here, but they're a little larger than needed. I sanded them down into shape, more or less, and they fit pretty well.

I carefully placed one of the half moon pieces about 1/4 inch inside the tube coupler, and tacked it into place with some thick CA. Then I placed a second half moon piece right up against it, and tacked that into place. I left space for a good fillet.

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This would be the forward end of the baffle. I coated the aft side of this double-thick piece with a good amount of JB weld, to hold it in place, and protect it from heat.

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The forward side of this piece got a good fillet of wood glue.

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I repeated this process with the aft baffle plate - two pieces, butted up against one another, filleted on the inside with wood glue, and coated and filleted on the underside with JB Weld.

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To help avoid making a mistake when I installed the baffle, I marked the forward and aft ends.

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Now you can see that the the baffle completely blocks ejection flames and particles, but allows the passage of air to pressurize the airframe. The forward sides of the plates are both filleted and the aft sides are coated with heat-resistant epoxy.

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If this works, then great! I've got an ejection baffle that doubles as a laundry shelf. If it fails, it won't be critical. I'll still probably put a piece of Nomex in the tube at least for the first flight, as a bit of insurance.
 
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lcorinth

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::Sigh::

Again, my pictures have disappeared, and dead links are here. Gimme a minute to figure out what was in the previous post, and I'll re-post the photos...
 

lcorinth

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The photos illustrating my previous post. No idea what happened here...

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lcorinth

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Next, I coupled the two body tubes together with the baffle/coupler. As I marked the forward and aft ends of the baffle, I also marked the forward body tube, to avoid any confusion.

Installation was with Bob Smith 30 minute epoxy.

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BDB

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That reminds me of the payload section on the Estes Reflector.
The facecard advertises "Huge Payload Section!"

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The only difference is that you can open up the plastic transition and nose cone on the Ventris if you want more payload room. That's my plan for mounting a camera. With the balsa on the Reflector, you're limited to launching crickets.
 

lcorinth

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That reminds me of the payload section on the Estes Reflector.
The facecard advertises "Huge Payload Section!"

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True dat. I cut off a thin slice of the transition shoulder, and a bigger bit of the nose cone shoulder on my Reflector. I dry fit everything together to see if I could get a Jolly Logic in there. I had to drill out a little bit from the nose cone shoulder, and it just fit. I glued on the nose cone, and still have enough of the transition shoulder for it to stay on safely (though I use tape to get quite a tight friction fit).

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lcorinth

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Okie dokie, pokies, fin time!!

I used my Guillotine Fin Jig to make sure I got the fins on perpendicular to the rocket. The fin slots will assure you get the fins aligned with the rocket body correctly, but it's still possible to have attach the fins not exactly perpendicular to the airframe (this happened on my first Partizon build).

I made sure I had the fins in straight up and down, then tacked them into place with some thick CA.

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Now I was able to stack the whole rocket and see what it looked like in person. It was exciting to see - this is a cool-looking rocket!

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Using a thin dowel, I did internal fillets with Bob Smith 30 minute epoxy. This was actually a little stressful. It was hard to get it in there without getting it everywhere, because even though I was using a thin dowel, there's just not that much space between the motor tube and the airframe. I had to clean up all the excess with alcohol and a paper towel, continually checking to make sure to clean up any epoxy that oozed over the end of the fin tabs.

I could simply have glued the fins in place with wood glue, but I wanted to try this internal fillet thing I'd read so much about. In the end, it turned out well - no excess epoxy where it didn't belong.

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Finally, I ran a ring of epoxy around the inside of the body tube, the outside of the motor tube, and on the aft ends of the fin tabs, and pushed the rear centering ring into place, making a tight fit against the fin tabs. I finished up with a fillet of epoxy on the aft end of the aft centering ring.

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Next up: I figure out what to use for rail button standoffs.
 

lcorinth

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By this point, I'd decided to use mini rail buttons from rail-buttons.com, for use with a 20mm launch rail. The balsa standoffs wouldn't cut it. I'd need something to drill into.

I got a suggestion from Rich of the Rich's Rockets blog: square dowel.

The balsa standoffs with the kit are about 1/4 inch high, if I remember correctly. So I got some 1/4 inch (if I remember correctly) square birch dowel and cut two lengths of about 3/4 inch long. My first attempt at cutting perfect 45 degree angles (see above Rich's Rockets link) with a razor saw didn't work out so well, because I don't have a miter box. So, I cut another piece.

Since I'm obsessed with trying to airfoil everything, I thought I'd see if I could do it with these. I marked a centerline using a piece of 1/8 inch fin stock. Since the line didn't hit the center of the dowel exactly, I flipped the standoff over and did two - so I had a centerline between two pencil lines. Then I marked rough guidelines for a rounded leading edge and tapered trailing edge. Then I began hand sanding.

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Results weren't perfect, but good enough.

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I wrapped coarse sandpaper around the airframe and sanded the standoffs back and for to make them conformal.

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I drilled two holes in the bottoms of the standoffs for better glue adhesion (I was later told this wasn't necessary with wood glue, but it's not going to hurt anything), then one pilot hole on top for the rail button screw.

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I followed that up with fillets of Bob Smith 30 minute epoxy filled with microballoons.

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Once the fillets were cured, I glued on the standoffs, at approximately the same spots as suggested in the kit instructions.

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Next up: Shock chord anchor attachment!
 

Scott_650

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Those stand-offs are just too cool! I'll be stealing that design for my Ventris - thank you very much.
 

lcorinth

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It was time to decide on how to mount the shock chord. I'd already done the Nike Smoke with the standard elastic, but then had a disaster with a smaller model where the elastic failed badly after about six flights. On the Leviathan, I went ahead and mounted an eye bolt to the forward centering ring and used nylon, but the centering rings on this rocket are so narrow.

I needed a way to mount the shock chord into the airframe. Then, someone on the NAR Facebook page posted something called a "shopping bag mount," which was basically a paper trifold mount with a loop of Kevlar instead of the shock chord itself. You tie the shock chord onto the Kevlar loop, and if need be, can cut it off and replace it when the shock chord wears out.

I used the paper mount from the Ventris kit, and a piece of Kevlar scavenged from an Apogee Aspire kit.

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Once I get a paper mount glued together and partially dry, I always run it around inside the tube to make it more conformal, to improve glue adhesion.

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Finally, I glue it into place (no idea how I got it so far inside the tube), and when it's dry, seal it down with another layer of wood glue.

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Scott_650

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That shock cord mount is pretty slick - another thing to happily steal ;-)
 

Cabernut

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I should have done something similar with my Ventris. I built it completely stock and after two flights the elastic is looking kinda ratty. G motors and elastic don't get along very well apparently. Now I have to get the x-acto out to replace it.

Are you going to use the stock shock cord or go with something else?
 

BDB

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I should have done something similar with my Ventris. I built it completely stock and after two flights the elastic is looking kinda ratty. G motors and elastic don't get along very well apparently. Now I have to get the x-acto out to replace it.
Me too. I was thinking about making a two-point harness attachment using kevlar and a coupler, but this looks like a viable alternative.
 

lcorinth

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I should have done something similar with my Ventris. I built it completely stock and after two flights the elastic is looking kinda ratty. G motors and elastic don't get along very well apparently. Now I have to get the x-acto out to replace it.

Are you going to use the stock shock cord or go with something else?
Now that I'm done with this weekend, I can get back to this thread.

In answer to your question, yes, I did use the stock chord. I was considering switching to some Kevlar rope I have, but a puff test told me that the recovery system would come out, no problem, so for the time being I stuck with the elastic.

That said, I have to note that the baffle I built into this rocket seems not to be sufficient. I flew it for the first time this weekend. Since I was using a Jolly Logic Chute Release, I wanted a bit more heat protection. I was going to use a piece of Nomex, but it was in a different rocket, so I threw some dog barf in there, just in case.

Despite the baffle and the dog barf, I got some minor burning on the chute and soot on the Chute Release. The Chute Release seems to still be working fine, but I'm going to put a sheet of Nomex in this rocket before flying again.

At least the baffle works as a laundry shelf, and partial heat protection. Just not as effective as I'd hoped.

OK, I'll be back shortly with more build photos.
 

lcorinth

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I just realized I never finished this thread.

Once the shock chord mount was installed, I needed to get the shock chord tied to it. It was pretty far inside, so I attached the shock chord to a clothes pin and carefully threaded it through the loop of the shopping bag mount.

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Then I turned the rocket upside down and shook the clothes pin back out.

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I thought I should tie something that would enable me to easily cut the shock chord if I wanted to change it, so I used a bowline.

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But I realized that a chute could really get caught on that, so I removed it. I eventually just tied a Duncan/Uni knot.

Turning to the transition, I had the idea that I might attach an 808 camera to it.

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I figured if I cut off the upper plastic loop, I could drill a hole in the payload tube and tape a camera on the slope of the transition. The camera would be downward-looking, but at an angle.

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I didn't end up doing that this time, so I just taped over the hole left by cutting the loop off. I wanted to keep any ejection gasses out of the payload tube and away from the altimeter.

Next, I filled the wood grain on the fins. Some people online suggested that this isn't really necessary with plywood, but I figured that if I didn't do it, I'd probably have to use more primer coats until I was happy enough with the smoothness of the fins, and I wanted to try something I'd read about.

I used a coat of Bondo Spot and Glazing Putty. Unfortunately, I can't seem to find a picture of it. Weird. I was sure I shot it.

Anyway, it worked great. Spread on with a putty knife, then sanded with 400 grit. Finally, I primed the booster and sanded. Here it is next to my Nike Smoke.

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The rocket was too tall to prime or paint all in one piece in my improvised booth, so I did the transition/payload section separately. Like with my Nike Smoke nose cone, I attached the transition to a PVC wand with some thick CA, then masked it off.

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K'Tesh

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Looking Good! Can't wait to see the footage you get.
 

Lowpuller

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I love a Ventris that's what I used for my L1.

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Cabernut

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Treat it well. Looks like the Ventris is now OOP. :(
 

lcorinth

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Payload section was primed.

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Because the nose cone was glued onto the payload tube, I wanted to seal the joint between the two. Access to the payload would be from the bottom. I like to seal permanent joints whenever I can, ostensibly for better laminar flow, but mainly because I think it looks better.

Here, for example, is my Astron Sprint XL, where I've smoothed the seam between the plastic tail cone and the body tube. I did this with thick CA over the primer, which I then sanded down smooth.

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I considered using CA for the Ventris, but apart from the Astron Sprint, I've had mixed results other times I've tried it. So I decided to try the Bondo Spot and Glazing Putty.

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While letting that cure, I took extra time to sand the booster and clean it up for final painting. I think I did two or three coats of primer, sanding between, because the first time or two, I didn't feel it was as smooth as I wanted it to be.

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Finally, I was ready for a base coat. I got out a can of Rust-Oleum 2X Semi Gloss (I had meant to buy Gloss, but got this by mistake. No big deal).

Got everything set up in the paint booth, aaaaand...

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...found I had accidentally grabbed a can of cottage cheese instead.

Here's what ended up on the base of the booth.

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And here's what ended up on my freaking rocket...

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Great. All that priming and sanding, and now I'd get to wet sand the rough paint off and try again with a new can.
 
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